Read and write power control methods and system for optical recording device

ABSTRACT

The present invention discloses read and write power control methods and system for an optical recording device that records information on an optical disk having read-only areas. The read and write power control methods respectively introduce the steps of determining a specific level of a former power control signal output based on a former power control, and then according to the specific level, setting a predetermined level of a power control signal to induce a present power control for rapidly outputting a proper power of the pick-up head. Accordingly, the level transition of the read/write power control signal can be shortened and even eliminated. An unstable read/write power output for the pick-up head can be avoided.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation application of patent applicationSer. No. 12/762,206, filed on Apr. 16, 2010 and now issued into U.S.Pat. No. 7,952,969, which is a division application of patentapplication Ser. No. 11/531,713, filed on Sep. 14, 2006 and now issuedinto U.S. Pat. No. 7,729,219, which claims the benefit of the filingdate under 35 U.S.C. §119(e) of a Provisional U.S. Patent ApplicationNo. 60/725,090, filed on Oct. 7, 2005, which is incorporated byreference herein.

BACKGROUND OF INVENTION

The present invention relates to read and write power control methodsand system of an optical recording device used for recording informationon an optical disk that had read-only areas.

Recently, various types of rewritable optical disk such as a DVD-RAM(Digital Versatile Disk Random Access Memory) or DVD-RW disks capable ofreproducing digital data therein have come into wide use. In DVD-RAMdisks, the stored information is consequently allocated in sector units.Each sector unit includes a read-only identification (ID) area (i.e. aheader) and a rewritable area (i.e. user data area), as shown in FIG.1A. The ID area, i.e. header, is embossed on the optical disk and can beread out with physical information data (PID) which is used to identifythe physical location of the sector relative to the optical disk.

Referring to FIGS. 1A & 1B, a pick-up head of an optical recordingdevice applicable for DVD-RAM disk might need to frequently meetmultiple headers disposed on the DVD-RAM disk as long as a writingsignal is set at logic high to order a write power for a recordingoperation of the pick-up head. Prior to meet each header, the writingsignal has to be set at logic low to temporarily switch the powercontrol from the write power induced by a write power control signal toa read power induced by a read power control signal. This could avoidcrushing the PID stored in the respective headers and proceed as thereading operations on the headers, as shown in FIGS. 1C & 1D. However,the pick-up head needs an exact and stable read power to accurately readout the relative PID from the respective headers.

Further referring to FIGS. 1C & 1D, each level transition of a read orwrite power control signal, under a turn of the power control, forexample, from either a write power to a read power, or from a read powerto a write power, would result in a unstable power output initially fora while. This is because the read/write power control loop needs aperiod P1, P2 to settle signal levels from an initial level to approachan optimal level. Especially, if a difference/drop between the initiallevel and optimal level becomes enlarged because of an operatingtemperature rise, after each time of beginning of writing operation, thelaser power emitted from the pickup head will be always unstable for awhile.

However, for the storage optical disk with a header layout, e.g.DVD-RAM, it is a significant topic to achieve a steady power control anda great reading and writing qualities during frequent read/write powerswitches.

In a case of performing a read power control during a recordingoperation, shown in FIG. 1C, an operation temperature that may besuccessively rising would cause in an inexact level difference L1 of theread power control signal output. The read power control signal outputhas to be adjusted by an Auto Power Control (APC) circuit withcompensating the read power control signal to approach the exact levelfor exactly reading data in the header. However a period of reading theheader is too short insufficient to sample an exact power signal into apower control loop to generate a proper power, especially in a high,multiple speed operation.

In another case of performing a write power control during a recordingoperation, shown in FIG. 1D, the write power control would be frequentlyinterrupted for each time when the pick-up head of the optical recordingdevice passes over respective headers on the optical disk and has to bereactivated thereafter. However, the level transition of a write powercontrol signal under different power control loop (i.e. a close or openloop) may be too long and insufficient to supply the pick-up head with asteady write power. Also, the operation temperature that may besuccessively rising would cause in an inexact level difference L2 of thewrite power control signal output. It is apparent that unstable writepower is greater proportioned to be involved in writing quality,especially under a high operation temperature.

SUMMARY OF INVENTION

To resolve those drawbacks, it is therefore a primary objective of thepresent invention to provide read and write power control methods andsystem for an optical recording device used for recording information ona corresponding optical disk having read-only areas, for example,DVD-RAM.

Secondly, it is an alternative objective of the present invention toprovide the read and write power control methods for an opticalrecording device capable of shortening level transition of the powercontrol signal, even eliminating the level transition, and preventing anunstable power output for the pick-up head.

Thirdly, it is an alternative objective of the present invention toprovide the read and write power control methods for an opticalrecording device capable of rapidly approaching an optimal level of thepower control signal to induce proper powerneeded by the pick-up head.

To achieve the foregoing objectives, the present invention provides aread power control method for an optical recording device having apick-up head. Before a start of a recording operation of the pick-uphead, a specific level of a former read power control signal based on aformer read power control (e.g. a close-loop control) is determined.After the recording operation, during the pick-up head passes overrespective header, a read power is rapidly induced by a predeterminedlevel of the read power control signal which is set under a present readpower control (e.g. an open-loop control) according to the specificlevel, and thereby shortening level transition of the read power controlsignal. Alternatively, if the present read power control is a close-loopcontrol during the pick-up head passes over respective header, the readpower can be rapidly induced by a predetermined level serving as aninitial level of the read power control signal; which is set accordingto the specific level, for gradually approaching an optimal level.

Furthermore, the present invention provides a write power control methodfor an optical recording device. During a recording operation of thepick-up head, a specific level of a write power control signal based ona former write power control is determined. When the pick-up head passesover respective headers, the former write power control is stopped.After the pick-up head passes over respective headers, a write power canbe rapidly induced by a predetermined level of a write power controlsignal which is set under a write power control (i.e. a close or openloop) according to said specific level of the former write power controlsignal, and thereby shortening level transition of the write powercontrol signal.

Furthermore, the present invention provides a power control system forread and power control of an optical recording device with a pick-uphead which includes a microprocessor that decides whether to proceed arecording operation or interrupt a recording operation. An encoderencodes a user data ready to be written in an optical disk and generatesa write signal for an auto power controller (APC). The auto powercontroller receives a feedback signal to detect a laser power emittedfrom the laser diode and receives the write signal from the encoder todecide a read or write power control. According to a specific level of aformer read power control signal based on a former read power control, aread power control signal level determiner determines a predeterminedlevel of a read power control signal output under a present read powercontrol. According to a specific level of a former write power controlsignal based on a fanner write power control, a write power controlsignal level determiner determines a predetermined level of a writepower control signal output under a present write power control.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1A illustrates a schematic signal diagram according to the relatedart showing a disk layout;

FIG. 1B illustrates a schematic signal diagram according to the relatedart showing a write signal;

FIG. 1C illustrates a schematic signal diagram according to the relatedart showing a read power control signal;

FIG. 1D illustrates a schematic signal diagram according to the relatedart showing a write power control signal;

FIG. 2 illustrates a flow chart of a read power control method accordingto the present invention;

FIG. 3 illustrates a flow chart of a write power control methodaccording to the present invention;

FIG. 4 illustrates a schematic diagram of a power control systemaccording to the present invention; and

FIGS. 5A-5D illustrate several schematic signal diagrams according tothe present invention showing an interrelationship among a disk layout(i.e. DVD-RAM) with headers, a write signal, a read power controlsignal, and a write power control signal.

DETAILED DESCRIPTION

Firstly referring to FIGS. 2, 5A, 5B, and 5C, a read power controlmethod of an optical recording device having a pick-up head forrecording information on a corresponding optical disk (e.g. DVD-RAM).The optical disk should be embossed with a plurality of read-only areasinterposed between the recordable areas, such as headers in DVD-RAM.According to a preferred embodiment of the present invention, the methodcomprises the following steps of:

In step S200, determining a specific level of a former read powercontrol signal output based on a former read power control (i.e. aclose-loop control) of the optical recording device, which induces aformer read power supplied before a recording operation of the pick-uphead starts for the corresponding optical disk;

In step S202, according to said specific level, setting a predeterminedlevel of a present read power control signal to a present read powercontrol (i.e. an open loop control). In an exemplar, before recordingoperation starts, the former read power is generated under a close loopcontrol. But during the pick-up head passes over respective header afterthe recording operation starts, the present read power is generatedunder an open loop control. Such a design that the open loop adapts thepredetermined level according to the specific level of the formerclose-loop control is capable of eliminating the level transition of theread power control signal and then preventing an unstable read poweroutput for the pick-up head. In other exemplar, if the former andpresent read power controls both belong to a close-loop control, thepredetermined level is utilized to serve as an initial level of thepresent read power control signal generated under the close-loop controlto gradually approach an optimal level for achieving a shorter settletime of the power control signal.

Meanwhile, the step of determining the specific level of the former readpower control signal based on the former read power control furthercomprises any one of the following steps of:

-   -   (1) Using a level of the former read power control signal, which        is gradually approached under the former read power control,        before the recording operation starts.    -   (2) Using a level of the former read power control signal, which        is sampled under the former read power control, before the        recording operation starts.    -   (3) Averaging a number of levels of the former read power        control signal achieved under the former read power control        within a specific operation period or a distance formed on the        optical disk before the recording operation starts.    -   (4) Filtering the former read power control signal by a low pass        filter (LPF) under the former read power control before the        recording operation starts.    -   (5) Calculating a level of the former read power control signal        generated by way of performing any of the aforementioned steps        (1), (2), (3) and (4) before the recording operation starts.    -   (6) Compensating a level of the former read power control signal        generated by way of performing any of the aforementioned steps        (1), (2), (3), (4) and (5) before the recording operation        starts.

In step S210, outputting a proper read power depending on thepredetermined level of the present read power control signal achievedfrom the step S202, under the present write power control, during thepick-up head passes over respective headers after the recordingoperation starts.

In step S220, optimizing the predetermined level of the read powercontrol signal by continuously updating the predetermined level duringeach non-recording state. In an exemplar of DVD-RAM, a non-recordingstate includes a called “writing and verifying” process. Basically, sucha verifying process is considered as a reading operation, and thereforethe predetermined level of the read power control signal output underthe respective read power control (i.e. an open-loop control) can becontinuously updated during each verifying process. Also, thenon-recording state can include a specific interval for activelyinterrupting the recording operation to update the predetermined level.Also, the non-recording state can include an interruption of therecording operation in response to rising of the operation temperatureof the optical disk in excess of a threshold level. At this moment ofthe interruption, the predetermined level of the read power controlsignal output under the read power control can be updated againstinvolvement of the rising temperature in level. Also, the non-recordingstate can include implement of an external interrupt recording controlfrom the outside of the system, which leads to update the predeterminedlevel of the read power control signal output under the read powercontrol for a stable power supply. For those recordings withoutverifying process, the non-recording state can include a stop recordingperiod when the pick-up head passes over a boundary between adjacentzones of a DVD-RAM disk, and the predetermined level of the read powercontrol signal output under the read power control can be updated. Also,the non-recording state includes implement of an internal interruptrecording control that will bring the read power control back to aclose-loop control for thereafter updating the predetermined level ofthe read power control signal output under the open-loop control.

Further referring to FIGS. 3, 5A, 5B, and 5D, the present inventionprovides a write power control method for the optical recording devicehaving a pick-up head for recording information on a correspondingoptical disk (e.g. DVD-RAM) with multiple headers allocated thereon. Thewrite power control method comprises the following steps of:

In step S300, determining a specific level of a former write powercontrol signal output based on a former write power control (i.e. aclose-loop control) of the optical recording device, which induces aformer write power supplied during a recording operation of the pick-uphead. In this embodiment of the present invention, the step ofdetermining the specific level of the former write power control signalbased on the former write power control further comprises any one of thefollowing steps of:

-   -   (1) Using a level of the foci er write power control signal        output which is gradually approached under the former write        power control.    -   (2) Using a level of the former write power control signal        output which is sampled under the former write power control.    -   (3) Averaging a number of levels of the former write power        control signal output which are achieved, within either a        specific operation period or a distance formed on the optical        disk, under the former write power control.    -   (4) By a low pass filter (LPF) or the like, filtering the former        write power control signal output which is achieved under the        former write power control.    -   (5) Calculating the level of the former write power control        signal output which is achieved by performing any one of the        aforementioned steps (1), (2), (3) and (4) to obtain the        specific level under the former write power control.    -   (6) Compensating the level of the write power control signal        output which is achieved by performing any one of the        aforementioned steps (1), (2), (3), (4) and (5) to obtain the        specific level under the former write power control.

In step S305, stopping the former write power control to switch off theformer write power during the pick-up head passes over respectiveheaders;

In step S310, according to said specific level, setting a predeterminedlevel of a write power control signal output to induce a start of apresent write power control (i.e. a close-loop control) after thepick-up head passes over respective headers. In one exemplar, if thepresent write power control belongs to a close-loop control, thepredetermined level is utilized to serve as an initial level of thispresent write power control signal output under the close-loop controlso as to gradually approach an optimal level for achieving a more properwrite power. In another exemplar, the present write power control canuse a close-loop control.

In step S320, generating a proper write power depending upon saidpredetermined level of the write power control signal output as long asa recording operation starts after the pick-up head passes overrespective headers.

Noted is that after the pick-up head passes over respective headers, theproper write power can be rapidly induced by the predetermined level ofthe write power control signal which is set under the present writepower control (i.e. a close or open loop control) according to thespecific level previously obtained, thereby shortening level transitionof the write power control signal, even eliminating the leveltransition, and preventing an unstable write power output for thepick-up head.

Further referring to FIG. 4, according to a preferred embodiment of thepresent invention, a power control system for controlling read and writepowers of an optical recording device with a pick-up head 50 forrecording information on an optical disk 10 with headers is introduced.The power control system includes a microprocessor 20, an encoder 30, anauto power controller (APC) 40, a read power control signal leveldeterminer 42 and a write power control signal level determiner 44. Themicroprocessor 20 decides whether to proceed on a recording operation orto interrupt a recording operation for updating a predetermined level ofthe read power control signal. The encoder 30 is operative to encodeuser data which is ready to be written in the optical disk 10, dependingon a write instruction from the microprocessor 20, and then generate awrite signal to the auto power controller (APC) 40. The auto powercontroller (APC) 40 according to a feedback signal from a front monitordiode (FMD) 22 of the pick-up head 50 to detect a power of a laser beamemitted from a laser diode (LD) 54. The power of the laser beam iscontrolled with a LD driver 52 of the pick-up head 50 based on the reador write power control signals. The auto power controller (APC) 40,according to the write signal from the encoder 30, decides to switcheither a read power control or a write power control as shown in FIG. 5.The auto power controller (APC) 40 utilizes some power controls (i.e. aclose loop and/or an open loop control) to respectively output a levelof a read/write power control signal for different requirements. Theread power control signal level determiner 42 determines a specificlevel which is achieved based on a former read power control, and thenaccording to specific level, sets either an initial level of a presentread power control signal output under the close-loop control forrapidly approaching an optimal level thereafter, or a predeterminedlevel of a present read power control signal output under the open-loopcontrol. The write power control signal level determiner 44 determines aspecific level which is achieved based on a former write power control,and then according to the specific level, sets a predetermined level asan initial level of a present write power control signal output under apresent write power control (i.e. a close-loop control) for rapidlyapproaching an optimal level thereafter.

Referring to FIGS. 5A-5D, several schematic signal diagrams according tothe preferred embodiment of the present invention show aninterrelationship among a disk layout (i.e. DVD-RAM) with disposal ofheaders, a write signal, a read power control signal, and a write powercontrol signal. Although the rising operation temperature may cause alevel difference L3 of the read power control signal output and/or alevel difference L4 of the write power control signal output, initially,as shown in FIGS. 5C and 5D. By the specific level f the former readpower control signal achieved under the former close-loop control beforethe recording operation starts, the predetermined level of the presentread power control signal output can be rapidly generated under thepresent open-loop control to induce a proper read power during thepick-up head passes over a header, thereby minimizing involvement ofrising operation temperature, and even eliminating the level transition.Alternatively, by the specific level of the former write power controlsignal approached under the former close-loop control, the predeterminedlevel of the present write power control signal output is set to serveas an initial level for rapidly approaching an optimal level under thepresent close-loop control to induce a proper write power after thepick-up head passes over a head, thereby minimizing involvement of therising operation temperature and even eliminating the level transition.

Those skilled in the art will readily observe that numerousmodifications and alterations of the device may be made while retainingthe teachings of the invention. Accordingly, the above disclosure shouldbe construed as limited only by the metes and bounds of the appendedclaims.

1. A power control method for a pick-up head that accesses information on an optical disk with a plurality of read-only areas, comprising: determining a specific level of a former read power control signal output under a former read power control to set a predetermined level of a present read power control signal to induce a present read power control; determining a specific level of a former write power control signal output under a former write power control to set a predetermined level of a present write power control signal to induce a present write power control; and performing the present read power control during the pick-up head passes over the respective read-only areas of the optical disk or the present write power control.
 2. The method as claimed in claim 1, further comprising: receiving a feedback signal from the pick-up head for detecting a laser power emitted from a laser diode.
 3. The method as claimed in claim 2, further comprising: individually utilising either a close loop or an open loop to approach the predetermined level of the present read or write power control signal.
 4. The method as claimed in claim 1, further comprising: determining the specific level of the former read power control signal output under the former read power control to induce a start of the present read power control during the pick-up head passes over the respective read-only areas of the optical disk.
 5. The method as claimed in claim 1, further comprising: determining the specific level of the former write power control signal output under the former write power control to induce a start of the present write power control during a recording operation of the pick-up head after the pick-up head passes over the respective read-only areas.
 6. A power control method for a pick-up head that accesses information on an optical disk with a plurality of read-only areas, comprising: determining a specific level of a former read power control signal output under a former read power control, and then using the determined specific level to induce a start of a present read power control during the pick-up head passes over the respective read-only areas of the optical disk.
 7. A power control method for a pick-up head that accesses information on an optical disk with a plurality of read-only areas, comprising: determining a specific level of a former write power control signal output under a former write power control to induce a start of a present write power control during a recording operation of the pick-up head after the pick-up head passes over the respective read-only areas. 